In recent years, many image forming apparatuses mounted with a plurality of receiving trays for loading sheets with an image formed by an image forming portion are manufactured so as to be able to separate and discharge the sheets for each job. In such a plurality of receiving trays, for example, as in the sheet discharge apparatus disclosed in Japanese Patent Application Publication No. 2004-284773, at least one receiving tray may be of a movable type. By doing this, the amount of storage and discharge sheets can be increased.
In a sheet discharge apparatus having such a movable receiving tray, when sheets are discharged to the receiving tray, the end of each discharged sheet slides in contact with the top of the sheet discharged already on the receiving tray. Therefore, due to the contact-sliding, the already-discharged sheet moves, thus a problem arises that sheets cannot be stacked in array on the receiving tray. Particularly, in a stapled sheet bundle, the stapled portion is projected, so that those portions interfere with each other. Therefore, whenever a succeeding sheet bundle is discharged, the discharged sheet bundle is pressed out from the receiving tray, thus the stacking in array is disturbed.
On the other hand, in the aforementioned sheet discharge apparatus disclosed in Japanese Patent Application Publication No. 2004-284773, in order to stack discharged sheets in array, at the base end of the movable receiving tray, a plurality of holding members for holding the back-end portion of the discharged sheets are installed. The holding members are installed on the rotary shaft rotating for driving which is directed in the perpendicular direction to the sheet discharge direction. When the rotary shaft rotates for driving, the holding members also rotate and hold the back-end portion of the sheets.
However, in the aforementioned constitution, the holding members are installed on the rotary shaft, so that the holding operation is limited to the neighborhood of the position of the rotary shaft and when the height of the movable receiving tray at the time of standby is different for each job, it is difficult to perform the holding operation. Furthermore, a driving apparatus for driving the rotary shaft is necessary, so that in the respects that the structure of the sheet holding mechanism is complicated and the cost of the apparatus is increased, there is a room for improvement left.
Further, the holding members rotating to hold sheets change the rotational angle due to the height of the uppermost sheet. When the sheets are high and the rotational angle is small, there is a fear that the sheet holding surfaces of the holding members may hit on the sheets so as to press them out.